1. Field
The slot machine according to one or more aspects of the present invention relates to a slot machine that executes a free game, in addition to a base game, when a predetermined condition has been satisfied during the base game.
2. Description of Related Art
Conventionally, in a slot machine, which is one type of a gaming machine, a game is started by inserting coins, or the like, in the gaming machine. In the game, a symbol string is variably displayed in a predetermined area in the gaming machine, and after the lapse of a predetermined period of time, the symbol string is stopped and displayed. Then, a payout is awarded based on a combination of the symbols thus stopped.
Generally, whether or not a winning combination for which a payout is awarded is established is determined depending on whether a predetermined number of the same kind of symbols (for instance, “CHERRY” and “7”) are positioned along a pay line set in advance. Conventionally, if a predetermined number or more of the same kind of symbols are positioned, a payout was also awarded based on the number of symbols thus positioned, irrespective of the pay line.
A large number of conventional slot machines execute two kinds of games, including a base game and a free game. The base game is executed by consumption of a gaming value (coins, credits, etc) corresponding to a bet amount. Alternatively, the free game is executed without consumption of any a gaming value corresponding to the bet amount. Switching from the base game to the free game occurs if a predetermined condition is satisfied, such as the case that a specific symbol(s) is(are) stopped and displayed during the base game. Switching from the free game to the base game occurs if a predetermined condition is satisfied, such as the case that a free game has been carried out by a predetermined number of times.
Further, in a conventional slot machine, the sense of expectancy of the player for a free game is improved by making it easier to establish a combination for which payout is awarded in the free game, as compared to the case of the base game. The specification of U.S. Pat. No. 6,394,902B1 discloses a slot machine in which a total of 15 symbols (3×5) are displayed by employing a video reel. In such a conventional slot machine, the symbol string which is positioned on the reel in the free game is changed from the one used in the base game, and the number of kinds of symbols is reduced from 8 kinds to 5 kinds. Thus, the probability for establishment of a combination for which a payout is awarded during the free game can be apparently increased.
However, in the above-described conventional slot machine, the kind and number of symbols must be changed in the base game and in the free game. Thereby, the this invention can be applied only to a slot machine using video reels. In other words, this technology could not be applied to a slot machine using mechanical reels on the periphery of which the kind and number of symbols were drawn in advance.
In the above-described conventional slot machine, when the kind and number of symbols are changed, a symbol lottery program and a reel control program which differ between the base game and the free game must be executed. This increases the processing load on the processor. Further, changing of the kind of symbols in the base game and the free game requires twice the memory capacity for storing image data corresponding to the symbols.
The object of the present invention is to provide a slot machine in which a higher payout is awarded in a free game, than in the base game, when a first symbol has been positioned in the free game. This makes it possible to reduce the processing load on the processor and minimize the memory storage area, while increasing the sense of expectancy of the player with respect to a free game.